ADDISON, Maine — The hum of the outboard motor provided background music as Capt. Paul Ferriero slid his 16-foot boat through the salt marshes of the Pleasant River this week.

A lifelong fisherman, Ferriero offers a two-hour salt marsh tour on the Pleasant River to boost what he makes catching lobster.

The trip is quite magical: no humans, no sign of civilization, no interruptions save the call of kingfishers or the shout of eagles. It is a transitional trip — a meeting of the aquatic and terrestrial.

Even Ferriero said the trip was recreational for him since he spends most of his time lobstering.

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But lobster fishing doesn’t pay all the bills and Ferriero, like most lobster fishermen, has to diversify. He moves yachts and offers tours, mostly on the open sea, showing tourists what lobster fishing is all about.

The tours he offers up the Pleasant River show a different side of the coast — the raw wilderness and incredible ecosystem that is contained in a salt marsh.

The grasses in the marsh are a dozen different shades of green —- from a bright lime to a slivery blue — and are the very reason these shores were settled. When farmers first arrived Down East, the grasses were harvested for livestock.

They are sometimes called tidal marshes, because they occur in the zone between low and high tides. Salt marshes provide nursery areas for fishes, shellfish, and crustaceans. These plants have extensive root systems which enable them to withstand brief storm surges, buffering the impact on upland areas, according to the Encyclopedia of the Earth.

Salt marshes also act as filters. Tidal creeks meander through the marshes transporting valuable nutrients as well as pollutants from upland development. The marshes can absorb or trap some of these pollutants, reducing the pollutant load entering estuaries. Salt marshes also prevent sediments from washing offshore, often creating more land on which salt marshes can grow.

As the boat glides softly through the marsh, Ferriero said the whole river valley is listed in resource protection. The waters teem with alewives and smelt and there are still wild Atlantic salmon. Passengers can often see deer, coyote, osprey, kingfishers, and moose.

“The eagles have had a tremendous year,” Ferriero said. Sure enough an adult eagle is sited, perched atop a tall pine. Moments later the calls of two immature eagles belie their positions nearby.

And the boat falls quiet, passengers enjoying the beauty, the sounds, the salty smell.